Recently, the use of a sheet-like pneumatic tire inner liner obtained from a thermoplastic resin or a thermoplastic resin composition of a thermoplastic resin blended with an elastomer, has been proposed and studied (Japanese Unexamined Patent Application Publication No. 2009-241855).
When actually using a sheet-like object obtained from the thermoplastic resin or the thermoplastic resin composition of a thermoplastic resin blended with an elastomer in a pneumatic tire inner liner, normally a manufacturing technique of winding a laminate sheet of the sheet obtained from the thermoplastic resin or the thermoplastic resin composition of a thermoplastic resin blended with an elastomer and a rubber (tie rubber) sheet that undergoes vulcanizing adhesion to the sheet-like object obtained from the thermoplastic resin or the thermoplastic resin composition of a thermoplastic resin blended with an elastomer, onto a tire molding drum, performing a lap splice, and then supplying to the tire vulcanization molding process is performed.
However, when a tire is manufactured by winding the abovementioned laminate sheet into a roll winding body, pulling and cutting the laminate sheet into portions of a required length, then winding the cut lengths onto the tire molding drum for lap splicing and then performing vulcanization molding, separation may occur between the sheet obtained from the thermoplastic resin or the thermoplastic resin composition that constitutes the inner liner, and the tie rubber sheet for vulcanizing adhesion with the sheet obtained from the thermoplastic resin or the thermoplastic resin composition, after the tire has started traveling.
When explained with reference to a drawing as illustrated in FIG. 2A, a laminate sheet 1, in which a sheet 2 obtained from a thermoplastic resin or a thermoplastic resin composition of a thermoplastic resin blended with an elastomer is laminated with a tie rubber layer 3, is cut into certain sizes (lengths) with a blade or the like and then lap-spliced on a tire molding drum so that a ring-like lap splice portion S is formed at both end parts of the laminate sheet 1. When one laminate sheet 1 is used, both end parts are lap-spliced so that a ring shape is formed, and when a plurality of laminate sheets 1 are used, the mutual end parts of each of the laminate sheets 1 are lap-spliced together so that one ring shape is formed with the plurality of sheets.
Next, other parts (not shown) required for tire manufacturing are wound and the tire undergoes vulcanization molding with a bladder.
After the vulcanization molding, an inner liner layer 10 is formed including the tie rubber layer 3 and the sheet 2 obtained from the thermoplastic resin or the thermoplastic resin composition of a thermoplastic resin blended with an elastomer, and an exposed portion and a portion embedded in the tie rubber layer of the sheet 2 obtained from the thermoplastic resin or the thermoplastic resin composition are formed in the vicinity of a lap splice part S as illustrated in FIG. 2B.
The phenomenon of the sheet 2 obtained from the thermoplastic resin or the thermoplastic resin composition and the vulcanizing-adhered tie rubber sheet 3 separating is produced where the sheet 2 obtained from the thermoplastic resin or the thermoplastic resin composition is exposed and at a distal end part vicinity 4, and the phenomenon first involves a crack being produced and the crack growing so that the phenomenon of the separation of the sheet 2 continues to grow.
While the above explanation describes the use of the laminate sheet 1 obtained from the tie rubber layer 3 and the sheet 2 obtained from the thermoplastic resin or the thermoplastic resin composition, as the inner liner layer, the same can be said when the laminate sheet 1 is used as a member other than the inner liner layer such as, for example, a reinforcing sheet layer (not shown) disposed over the entire circumferential direction on the tire external periphery side of the inner liner layer. In particular, tire locations in which the laminate sheet is disposed as the reinforcing sheet layer are normally used under severe conditions such as when a load is applied repetitively over a long period of time and these locations often suffer from the problems of the occurrence of cracks and/or separation.